JPS598234B2 - thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head having a thin film heating resistor made of hafnium boride and oxygen, and also to a method for manufacturing the same.

A thermal head used for thermal print recording has a plurality of heat generating resistors on a substrate with electrical insulation and a smooth surface, such as glass, and an electric conductor for supplying power to the heat generating resistors. Recording is performed by applying a current to the corresponding heat-generating resistor through an electric conductor to generate heat, and contacting the recording medium with a corresponding heat-generating resistor so as to obtain the necessary thermal pattern according to the information to be recorded. be.

Heat generating resistors used therein include conventional thin film heat generating resistors such as tantalum nitride and dichrome tin oxide, thick film heat generating resistors using silver-palladium, etc., and semiconductor heat generating resistors using silicon semiconductor. Among these, thermal heads using thin film heating resistors have better thermal response, superior heat resistance and thermal shock resistance, longer lifespan, and higher reliability than thick film heating resistors, semiconductor heating resistors, etc. It has the following characteristics.
Conventionally, tantalum nitride has been used for this thin film heating resistor, which has excellent heat resistance, high reliability, and has a specific resistance value of 250 to 3.
00 μΩ? This is a relatively high value and the controllability of manufacturing is also high.
Especially often used. However, tantalum nitride is about 3
At high temperatures of 00° C. or higher, it is rapidly oxidized and its resistance value increases rapidly, which has the disadvantage of deteriorating print density when printing on recording paper.

Generally, silicon oxide (SiO2) is used to compensate for this drawback.
) with an oxidation-resistant protective layer of tantalum oxide (
Although a wear-resistant layer of Ta2O5) is provided and used as a thermal head, the change in resistance when the thermal head is operated for a long time is still not fully satisfactory. Particularly in recent years, as the demand for high-speed thermal heads has increased, it is necessary to shorten the current pulse width of the head to color the thermal paper, and the heating resistor becomes even hotter, resulting in a shorter lifespan. Therefore, there is a need for a more heat-resistant antipyretic antibody. In addition, the area resistance of tantalum nitride is usually around 50Ω/hole, and even when it is made especially large as a thermal head, it is about 100Ω/hole, and in order to further increase the resistance value, it is necessary to perform trimming or increase the film thickness. Although methods such as thinning are used, there are disadvantages such as complicating the manufacturing process and adversely affecting the lifespan. As described above, the tantalum nitride thin film heating resistor cannot have a large sheet resistance, so in order to supply enough power to heat the resistor, a large current is inevitably required, and the resistance value of the electric conductor becomes a problem.

In other words, since the resistance value of the electric conductor cannot be ignored compared to the resistance value of the thin film heating resistor, the amount of heat generated by each resistor will differ due to the difference in the distance of each electric conductor connected to the resistor, and the recording pattern will be different. There will be a difference in density between the images and the recording quality will be poor. Furthermore, if the size of the thin film heating resistor is reduced in order to increase the recording density, the sheet resistance value of the thin film heating resistor remains unchanged and only the resistance value of the electrical conductor increases, so power consumption in the electrical conductor becomes a problem. Furthermore, if the thickness of the electrical conductor is made extremely large in order to avoid this, in the case of multi-layer wiring, the surface becomes extremely uneven and becomes susceptible to abrasion, resulting in major structural problems. Also, if the current is large, it is a heating power source,
Inconveniences arise, such as the need to increase the capacity of switching circuits and the like. The present invention improves the above points and provides a thermal head using a thin film heating resistor that is resistant to oxidation, has a stable resistance value, and allows the specific resistance to be selected up to a high value.
Its feature lies in the heating resistor made of hafnium boride and oxygen. In this heating resistor, hafnium boride and oxygen are mixed on an atomic scale. A detailed explanation will be given below with reference to the drawings.

FIG. 1 is a sectional view of a main part of an example of the shape of a thermal head applied to the present invention.

Reference numeral 1 in the figure is a substrate made of an electrical insulator such as ceramics, glass, or crystal ceramics. 2 is a thin film heating resistor according to the present invention made of hafnium boride and oxygen.

Reference numeral 3 denotes an electric conductor for supplying power to the thin film heating resistor, which is made of a good electric conductor such as aluminum or gold.

4 is a protective layer for the thin film heating resistor and electric conductor, for example, a multilayer structure made of silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, or a combination of these, manufactured by electron beam evaporation, sputtering, etc.; This makes it possible to further extend the life of the thermal head. The thin film heating resistor made of hafnium boride and oxygen of the present invention can be manufactured by either sputtering or electron beam evaporation. A method of sputtering a target of boron and hafnium metal at the same time, a method of sputtering a target of boron and metal hafnium, a method of sputtering a target of argon, oxygen,
There is a method of performing active sputtering in an atmosphere containing diborane.

When hafnium boride is used as a target, it can be used as a target by placing hafnium boride in a powdered or pressed state on a quartz plate, for example, but it is necessary to sinter it in advance by vacuum hot pressing at 1100°C or higher. It is easier to control sputtering if a target is used.

Further, when boron and metal hafnium are to be targeted at the same time, boron and metal hafnium can be mixed, or one can be embedded in the other or placed on a part of the surface. 1×10-3T0rr in either case
It is best to carry out in a mixed atmosphere of argon and oxygen of ~5X10T0rr, preferably 1X10T0rr~1x1
0-1T0rr is good. In addition, when performing active sputtering in a mixed atmosphere of argon, oxygen, and diborane with metal hafnium as a target, the total gas pressure is 1×10
-2T0rr~5×10-1T0rr1 preferably 1×
10-2T0rr~5×10-2T0rr1 Among them, the partial pressure of diborane is 1-10% of the total pressure, preferably 2-6
%.

During any of the above sputtering processes, by selecting the oxygen partial pressure in the atmosphere from 0.1 to 10%, oxygen is added to the heating resistor at an atomic ratio of 0.00% to 0.00% of hafnium.
5 or more can be contained.

If the oxygen content is too low, it will not be effective, and if it is too high, it will be difficult to control the resistivity and the heat resistance will be poor. 0
5 to 0.6 is more preferable, and 0.1 to 0.3 is most preferable. The specific resistance value of the heating resistor created in this way is
200μΩ? ~5000μΩ? It is possible to select up to When producing a heating resistor by electron beam evaporation, a tablet is made by pressing hafnium boride powder at a pressure of about 100k9/(-Fil or higher) and the tablet is heated in advance at a constant temperature in a high vacuum of 1×10-4T0rr or higher. It can be deposited on a substrate kept at a constant temperature.

At this time, the oxygen content in the heating resistor is adjusted to 0.005 to 1.0 (atomic ratio) of hafnium by introducing a gas containing oxygen into the electron beam evaporation using a needle valve or the like. I can do it. The thin film heating resistor created in this way is made of hafnium boride and oxygen (contains C, N, etc. as impurities), and if the specific resistance value is set high, the resistance value of the electrode part will be high to some extent. The manufacturing process is easy because the electrodes are thin, and the surface irregularities are reduced by making the electrodes thinner, thereby improving wear resistance.

In addition, since the voltage drop at the electrode portion is negligible, uneven color density due to uneven heating of the thin film heating resistor is also reduced, and electrode patterns such as matrix wiring can be designed more freely. Furthermore, by heating the substrate to 200 to 500 degrees Celsius during sputtering or electron beam evaporation, the adhesion between the substrate and the thin film heating resistor is improved, which is effective in improving the stability of the film.

Next, an explanation will be given based on an example.

Example 1 Using a target of 5 inch diameter hafnium boride HfB2 (manufactured by Ventron, USA, purity 99%) hot pressed at 1100°C, thoroughly cleaned glass with a thickness of 50 pm was used.
While heating the crusted alumina substrate to 300℃, the argon pressure was 4×10−2T0rr and the oxygen pressure was 3×10−
High frequency bipolar sputtering was performed in a 3T0rr1 mixed gas atmosphere.

Spatter rate is 200X/min, input power is 3.0W/c
! After sputtering for 5 minutes at 100 Å, a thin film heating resistor with a film thickness of 1000 A was obtained. Is the specific resistance 1200μΩ? ,
The sheet resistance was 120Ω/mouth. When the composition of this film was examined using an ion microanalyzer, it was found that 0.3 (atomic ratio) of hafnium was contained in oxygen. Titanium 10 on this
A1 aluminum was applied by electron beam evaporation to a thickness of 1 μm, and a thermal head pattern with a resolution of 4 lines/mm was formed by selective etching, and this was designated as thermal head A.
Furthermore, silicon oxide (SlO2) is applied as a protective layer on top of this.
A 1 μm layer of tantalum oxide (Ta2O5) was continuously laminated by sputtering to form a thermal head A2. For comparison, tantalum was targeted by high-frequency bipolar reactive sputtering, and the partial pressure of argon and nitrogen was 8.
×10-2T0rr1 Nitrogen partial pressure is 1×10-4T0rr
A thermal head B1 of a tantalum nitride thin film heating resistor having a thickness of 1000 A was prepared under the following conditions.

This tantalum nitride thin film heating resistor has a specific resistance of 260 μΩ.
? The area resistance was 26Ω/mouth. Thermal head B
1, silicon oxide (SiO2
) was continuously laminated with 10 μm of tantalum oxide (Ta2O5) by sputtering to form a thermal head B2.
These thermal heads were subjected to an acceleration test using a 50 Hz, 6 ms rectangular wave while increasing the power by 1 W/7nd every 30 minutes. The results are shown in FIG.
As is clear from the figure, it was found that the thermal head having a thin film heating resistor produced by the manufacturing method according to the present invention can withstand high applied power and has little change in resistance at high temperatures. In other words, while the comparative example is difficult to put into practical use without a protective film, the thermal head according to the present invention can be put into practical use without a protective film, and when a protective film is attached, very good heat resistance can be obtained. Example 2 Using a 6-inch diameter hafnium boride (HfB2) target hot-pressed at 1,300°C, a thoroughly cleaned 50-pm-thick crystal alumina substrate was heated for 20 minutes.
Heat the substrate to 0°C and apply an argon pressure of 4 x 10-2T0r.
Two-pole sputtering was performed in a mixed gas atmosphere with an r1 oxygen pressure of 4×10 −3 T0rr.

Spatter rate is 200A/min, input power is 3.0W/
After sputtering with 011 for 3 minutes, a thin film heating resistor of the present invention having a film thickness of 600A was obtained. Specific resistance is 2100μ
The sheet resistance was 350Ω/mouth. This vanadium 10x1 aluminum was applied by 1 μm electron beam evaporation, a thermal head pattern with a resolution of 4 lines/Mm was formed by selective etching, and silicon oxide (SiO2) was added on top of this as a protective layer to 2 μm 1 aluminum oxide (Al2O3). 5μm continuous sputtering,
I made a thermal head. When this thermal head was subjected to the same acceleration test as in Example 1, good results similar to those of thermal head A2 were obtained.

Example 3 A target was used in which a large number of sintered 1/4 inch diameter boron plates were placed on a 6 inch diameter metal hafnium plate so that the surface area ratio of metal hafnium to boron was approximately 1:2. .

500 pieces of thoroughly cleaned claest ceramic substrates
Heating the substrate to ℃ and argon pressure: 3 x 10-2T0rr1
At an oxygen pressure of 2 x 10-3T0rr, R. F. It sputtered on two poles. When sputtering was carried out for 8 minutes at a sputtering rate of 100 A/min, a thin film heating resistor with a film thickness of 800 A, a specific resistance value of 1040 .mu..OMEGA., and a sheet resistance of 130 .OMEGA./hole was obtained.
o After evaporating titanium and 10A1 aluminum with a 1μm electron beam on top of this, selective etching was performed to form 4 pieces/M7! L
A thermal head pattern with high resolution was formed.

Next, 10pm of magnesium oxide (MgO) was added as a protective film.
were laminated with spatter. When this thermal head was subjected to the same acceleration test as in Example 1, it was found to be 23.5W/
M77! The resistance change rate was within ±2%, and very good results were obtained compared to thermal heads using tantalum nitride. Example 4 A 6 inch diameter metal hafnium plate was used as a target.

400 ml of thoroughly cleaned claest ceramic substrates
The substrate was heated to ℃ and active sputtering was performed in an atmosphere of a mixed gas of argon, diborane, and oxygen. Argon +
The total pressure of diborane + oxygen is 3.5 x 10-2T0rr1
Diborane partial pressure is 1.5X10-4T0rr oxygen partial pressure is 1
A film thickness of 1000X was formed using a high-frequency two-pole sputter at ×10-4. Area resistance is 50Ω/mouth (specific resistance value is 500
μΩCIrL). Add 100 vanadium on top of this.
After A1 gold was deposited with a 1 μm electron beam, a thermal head pattern with a resolution of 4 lines/mm was formed by selective etching. Next, aluminum oxide (Al
2O3) 10pm was laminated by sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, the resistance change rate was within ±2% up to 24 W/Md. This example also gave much better results than the thermal head using tantalum nitride in the comparative example. Example 5 A tablet was made by pressing hafnium boride powder at a pressure of 100 kg/Cll or more, and the tablet was heated to 300°C on a creste ceramic substrate that had been thoroughly cleaned in advance.
After vacuuming to a vacuum level of 2 x 10-5T0rr, the vacuum level was increased to 5 x 10-5 while introducing dry air with a needle valve.
Electron beam deposition was performed at 6T0rr to a thickness of 1000X.

This area resistance is approximately 70Ω/mouth (specific resistance value is approximately 700μ
ΩCTL). Next, after evaporating titanium and 10A1 aluminum using a 1.5μm electron beam,
After forming a pattern with a resolution of 4 lines/MlL by selective etching, 1 μm of silicon oxide (SiO2) was formed.
A thermal head was prepared by continuously laminating 10 Pm of tantalum monoxide (Ta2O5) by sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, good results similar to those of thermal head A2 were obtained. When the composition of this film was investigated with an ion microanalyzer, it was found that oxygen was .21 (contains atom O.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an example of the shape of a thermal head according to the present invention. FIG. 2 is a characteristic diagram showing the effects of the present invention. 1...Substrate, 2...Thin film heating resistor. 2... Electric conductor, 4... Protective layer.

Claims (1)

[Scope of Claims] 1. A thermal head having a substrate, a heating resistor formed on the substrate, and an electric conductor for supplying power to the heating resistor, in which the heating resistor is made of hafnium boride and oxygen. A thermal head comprising: 2 The oxygen content in the heating resistor is 0 of hafnium.
．． 005 (atomic ratio) or more, the thermal head according to claim 1. 3 The oxygen content in the heating resistor is 0 of hafnium.
．． The thermal head according to claim 1, wherein the atomic ratio is 01 to 1.0 (atomic ratio). 4. The thermal head according to claims 1 to 3, wherein the heating resistor is covered with a silicon oxide thin film. 5 Claim 1 having a tantalum oxide protective film
The thermal head according to items 1 to 4. 6. The thermal head according to claims 1 to 4, which has a protective film of aluminum oxide. 7. The thermal head according to claims 1 to 4, which has a protective film of magnesium oxide. 8. A method for manufacturing a thermal head, characterized in that a heating resistor made of hafnium boride and oxygen is manufactured by sputtering. 9. The manufacturing method according to claim 8, wherein sputtering is performed in a mixed gas containing argon and oxygen. 10. The manufacturing method according to claim 8 or 9, wherein the sputtering target is hot-pressed hafnium boride. 11. The manufacturing method according to claim 8 or 9, wherein metal hafnium and boron are arranged so as to be targets at the same time. 12. The manufacturing method according to claim 8, wherein sputtering is performed in a mixed gas containing argon, oxygen, and diborane. 13. The manufacturing method according to claim 12, which targets hafnium metal. 14. The manufacturing method according to claims 8 to 13, wherein sputtering is performed while heating the substrate at 200°C to 500°C. 15. A method for manufacturing a thermal head, characterized in that a heating resistor made of hafnium boride and oxygen is manufactured by electron beam evaporation. 16. The manufacturing method according to claim 15, wherein electron beam evaporation is performed while introducing a gas containing oxygen. 17 Claim 15 or 16 in which electron beam evaporation is performed while heating the substrate at 200°C to 500°C
Manufacturing method described in section.